I have a Genesis Datum that I built up from a frame. I bought a s/h shimano groupset and have a prob with the front mech......
When shifting from the small to the big front ring, the amount of force required at the lever is really high. There is minimal friction in the new cables. It seems to be because the cable run, the mech pivot and the arm the cable pulls on are all in a straight line. There is no mechanical advantage when you are trying to shift.
Does this mean that the front mech is the wrong type? Can I get a front mech with the activation arm that runs parallel to the BB, rather than the seat tube?
What derauleur do you have?
From Google:
* is it bottom pull?
* it one of the crop of long arm types?
* ie is it a Shimano Ultegra FD-R8000 Front Derailleur (or equivalent)
http://www.genesisbikes.co.uk/bikes/adventure/adventure/datum/datum-30
The R8000 Ultegra model or the FD-5801 105 model both use a linkage rather than long arm which is much more tolerant of less than ideal cable routing.
Alternatively, the mech you have has two cable routing options to suit varying cable entry angles. Shimano make a tool to identify which routing option should work best on any given set up.
TL-FD90 for 9000 Dura Ace, or TL-FD68 for 6800, 5800, and 4700 mechs.
Its an ultegra mech, im afraid I cant get to see the model number at the moment. Its an early 11sp I think. The arm that the cable attaches to is about 3cm long, and is vertical when the chain is on the small chainring.
Does this help?
That's a 6800.
You need to add an in-line barrel adjuster (unless you already have one) as the cable needs to be pretty well tensioned to shift those derailleurs.
Instructions here :-
6800 front mechs...
Is the cable routed correctly through the the mech.? As in over the little pin.? Have you got a front mech cable alignment tool.? Sounds daft but there is one and Shimano made it for a reason.
Is it braze on.? If so have you wound out the little grub screw that touches the frame.? This stops the mech from moving when shifting.
Are the pivots stiff.? The mech might be clean as a whistle but the pivots might need a spot lube.
Guys, thanks for all your help. I had no idea there was a front mech alignment tool or a method of adjusting the cable angle. I will check my cable routing.